System and method for calculation of capacity charts at a locked counterweight position

A crane control system comprising:

• a processor configured to implement computer executable instructions;
• a first input interface in communication with the processor and configured to receive an indication of a locked position of a variable position counterweight;
• a second input interface in communication with the processor and configured to receive an input corresponding to an operating condition indicative of a balance between a load on a crane boom and a variable position counterweight;
• a first output interface in communication with the processor and configured to output a control signal for controlling the position of the variable position counterweight;
• a second output interface in communication with the processor and configured to output an indication of a new capacity of the crane;
• and,
• a computer memory in communication with the processor and storing data representing a load chart and computer executable instructions, that when implemented by the processor cause the processor to perform functions comprising:
• calculate the control signal for controlling the position of the variable position counterweight based on keeping the input received at the second input interface at or below a maximum target value for the operating condition dependent on a balance of the crane between the variable position counterweight at a first distance from a center of rotation of the crane and a load on the hook;
• determine a maximum capacity of the crane at a hook position for the boom combination;
• calculate at least one new target value for the operating condition based on the indication of the locked counterweight position received over the first interface and dependent on the balance of the crane between the variable position counterweight at a second distance that is different than the first distance and the load on the hook;
• calculate a new capacity of the crane by decrementing the maximum capacity of the crane proportionally to a difference in the maximum target value and the at least one new target value;
• and,
• output an indication of the new capacity over the second output interface.

A crane comprising:

• an upper works;
• a boom mounted to the upper works at a first end and having a hook at a second end;
• a variable position counterweight horizontally extendable from the upper works;
• a counterweight movement device configured to move the variable position counterweight relative to the upper works;
• and
• a crane control system, comprising:
• a processor configured to implement computer executable instructions;
• a first input interface in communication with the processor and configured to receive an indication of a locked position of a variable position counterweight;
• a second input interface in communication with the processor and configured to receive an input corresponding to an operating condition indicative of a balance between a load on a crane boom and a variable position counterweight;
• a first output interface in communication with the processor and configured to output a control signal for controlling the position of the variable position counterweight;
• a second output interface in communication with the processor and configured to output an indication of a new capacity of the crane;
• and,
• a computer memory in communication with the processor and storing data representing a load chart and computer executable instructions, that when implemented by the processor cause the processor to perform functions comprising:
• calculate the control signal for controlling the position of the variable position counterweight based on keeping the input received at the second input interface at or below a maximum target value for the operating condition dependent on a balance of the crane between the variable position counterweight at a first distance from a center of rotation of the crane and a load on the hook;
• determine a maximum capacity of the crane at a hook position for the boom combination;
• calculate at least one new target value for the operating condition based on the indication of the locked counterweight position received over the first interface and dependent on the balance of the crane between the variable position counterweight at a second distance that is different than the first distance and the load on the hook;
• calculate a new capacity of the crane by decrementing the maximum capacity of the crane proportionally to a difference in the maximum target value and the at least one new target value;
• and,
• output an indication of the new capacity over the second output interface.